#include <stdio.h>

int main()
{
    char a = 0x71, b = 0xd0;
    unsigned char aa = 0x71;
    unsigned char bb = 0xd0;

    printf("%#x,%#x\n", a, b);               // 转 int 输出bai
    printf("%#x,%#x\n", 0xff & a, 0xff & b); // 取1字节输出

    printf("a = %d; b= %d\n", a, b);
    printf("aa = %d; bb= %d\n", aa, bb);

    return 0;
}